Global Attractor for a Nonautonomous Inclusion with Discontinuous Right-Hand Side

We consider a nonautonomous inclusion the upper and lower selectors of whose right-hand side are determined by functions with discontinuities of the first kind. We prove that this problem generates a family of multivalued semiprocesses for which there exists a global attractor compact in the phase space.     

Mechanical properties of the canine internal carotid artery under constant load regimes

Conclusions 1. A method was developed for the study of the mechanical properties of narrow blood vessels under intravascular pressure and axial stretching.2. A real difference in the deformative properties of the individual segments of the canine internal carotid artery was found experimentally.3. It follows from the analysis of the experimental data that, under identical tension levels within the normal physiological range, the mechanical properties in the circumferential direction are similar in all the arterial segments.4. It was found that 30% more energy is required to deform the flexure of the canine internal carotid artery under its topographical and anatomic conditions than that required for the cervical, intraosseous, and intracranial segments of this artery.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 4, pp. 702–706, July–August, 1976.     

Autogenous vein transplants in reconstructive vascular surgery

The principal methods of reconstructive surgery of the main human blood vessels in the presence of segmentary atherosclerotic occlusions are considered; the chief assumptions made in investigating their mechanical properties are examined. Uniaxial and biaxial loading of the human great saphenous vein has shown that a diseased arterial segment could be replaced by an autogenous resected vein.     

Deformation of human abdominal aorta at biaxial tensioning

An experimental procedure is suggested for studying biaxial tensioning of soft biopolymeric material. The experimental data found at a monaxial and biaxial tensioning are compared.     

Changes in the mechanical properties of human coronary arteries with age

Conclusions We were the first to experimentally find that the greatest changes in E₂, E_2(K) ^tan, _2(K), and W_(K) of the human cardial coronary arteries are observed in people who have reached the age of 40 years. To compare the experimental data, all the parameters of the mechanical properties of the coronary arteries were determined at one and the same stress level — 0.01 kgf/mm², which on an average corresponds to an increased intravascular pressure of within 200 to 240 mm Hg. Under elinical conditions, this pressure is considered critical for arterial vessels affected by atherosclerosis. The most marked shifts in the changes of the mechanical properties were found in the superior part of the left coronary artery. At the age of 40, a considerable decrease in the deformability of the arterial walls in the circular direction is observed, and the walls become more rigid. At the same time, the vessel wall becomes thicker, especially because of increase in its internal layer — the intima. All this facilitates the development of intravascular thrombosis in people suffering from coronary sclerosis and leads to the development of acute stenosis, frequently exceeding 75% of the clearance area of the vessel, or to a complete obstruction of the superior part of the left coronary artery. If the inferior part of this vessel still retains a fair deformability, it is possible to perform a reconstructive operation, by means of which normal blood circulation is restored from the initial part of the ascending aorta to the inferior section of the corresponding coronary artery. From the experimentally found characteristics of the mechanical properties of the inferior parts of coronary vessels, we can select the best autoplastic material — a vessel segment derived from the patient himself — with properties similar to those of the affected vessel, which ensures the successful performance of such an operation, namely, the reconstruction of the human coronary vessels.Lecture delivered at the Third All-Union Conference on Polymer Mechanics, Riga, November 10–12, 1976.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 2,, pp. 277–282, March–April, 1977.     

Mechanical properties of the wall of the human abdominal aorta after endarterectomy

The deformation and strength properties of the wall of the human aorta have been studied after open endarterectomy. Specimens cut from the aorta wall and specimens subjected to endarterectomy at the levels of both the inner and outer elastic membranes were investigated. It was found that endarterectomy at the level of the inner elastic membrane does not affect the deformation properties of the wall but leads to an increase in strength as compared with the atherosclerotic wall. Endarterectomy at the level of the outer elastic membrane sharply reduces the deformability in the transverse direction as compared with the intact aorta.